U.S. patent number 7,622,007 [Application Number 10/549,933] was granted by the patent office on 2009-11-24 for substrate processing apparatus and semiconductor device producing method.
This patent grant is currently assigned to Hitachi Kokusai Electric Inc.. Invention is credited to Naoharu Nakaiso.
United States Patent |
7,622,007 |
Nakaiso |
November 24, 2009 |
Substrate processing apparatus and semiconductor device producing
method
Abstract
Disclosed is a substrate processing apparatus which comprises
reaction tubes (3,4) for processing multiple substrates (27), a
heater (5) for heating the substrates, and gas introducing nozzles
(6,7,8,9,10) for supplying a gas into the reaction tubes. Each of
the gas introducing nozzles (6,7,8,9) is structured so that at
least the channel cross section of a portion facing the heater (5)
is larger than those of the other portions.
Inventors: |
Nakaiso; Naoharu (Toyama,
JP) |
Assignee: |
Hitachi Kokusai Electric Inc.
(Tokyo, JP)
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Family
ID: |
34131387 |
Appl.
No.: |
10/549,933 |
Filed: |
August 5, 2004 |
PCT
Filed: |
August 05, 2004 |
PCT No.: |
PCT/JP2004/011266 |
371(c)(1),(2),(4) Date: |
September 11, 2006 |
PCT
Pub. No.: |
WO2005/015619 |
PCT
Pub. Date: |
February 17, 2005 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20070034158 A1 |
Feb 15, 2007 |
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Foreign Application Priority Data
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Aug 7, 2003 [JP] |
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2003-206526 |
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Current U.S.
Class: |
118/725; 118/715;
156/345.51; 156/345.52 |
Current CPC
Class: |
C23C
16/455 (20130101); H01L 21/67109 (20130101); C23C
16/45578 (20130101) |
Current International
Class: |
H01L
21/00 (20060101); C22C 16/00 (20060101); C23C
14/00 (20060101) |
Field of
Search: |
;118/715-733
;156/345.51-345.55 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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5-198517 |
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Aug 1993 |
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JP |
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8-213330 |
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Aug 1996 |
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JP |
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9-102463 |
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Apr 1997 |
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JP |
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2000-68214 |
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Mar 2000 |
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JP |
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2000-306916 |
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Nov 2000 |
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JP |
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2001-252604 |
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Sep 2001 |
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JP |
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2002-118066 |
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Apr 2002 |
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JP |
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2002-353211 |
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Dec 2002 |
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JP |
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2003-017422 |
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Jan 2003 |
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JP |
|
2003-45811 |
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Feb 2003 |
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JP |
|
2003-45864 |
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Feb 2003 |
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JP |
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2003045811 |
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Feb 2003 |
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JP |
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2004-134466 |
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Apr 2004 |
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JP |
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2005-286005 |
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Oct 2005 |
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JP |
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WO-00/15868 |
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Mar 2000 |
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WO |
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WO-2004/034454 |
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Apr 2004 |
|
WO |
|
Primary Examiner: Kackar; Ram N.
Attorney, Agent or Firm: Birch, Stewart, Kolasch &
Birch, L.L.P.
Claims
The invention claimed is:
1. A substrate processing apparatus, comprising: a reaction
container to process a plurality of substrates; a heater to heat
said plurality of substrates; and a plurality of nozzles having
different lengths through which reaction gas is to be supplied into
said reaction container, wherein each of said plurality of nozzles
includes a horizontal portion extending in a horizontal direction
and a vertical portion rising in a vertical direction, said
horizontal portion is attached to a sidewall of said reaction
container with said horizontal portion penetrating the sidewall of
said reaction container, said vertical portion is disposed in said
reaction container apart from an inner wall of said reaction
container such that a portion of the vertical portion is opposed to
said heater, a flow-path cross-sectional area of the portion of
said vertical portion that is opposed to at least said heater is
greater than a flow-path cross-sectional area of said horizontal
portion, and a flow-path cross-sectional shape of the portion of
said vertical portion that is opposed to at least said heater is
formed into a substantially elliptic shape with a short axis
thereof oriented toward a central portion of the substrate.
2. A substrate processing apparatus as recited in claim 1, wherein
said cross-sectional shape of the horizontal portion of said nozzle
is formed into a circular shape.
3. A substrate processing apparatus as recited in claim 1, wherein
said heater is divided into a plurality of heater zones, and when
said substrate is processed, temperatures in the reaction container
corresponding to the respective heater zones are maintained at the
same temperatures.
4. A producing method of a semiconductor device, comprising:
transferring a plurality of substrates into a reaction container;
processing the plurality of substrates by supplying reaction gas
into the reaction container heated by a heater through a plurality
of nozzles having different lengths, each of said plurality of
nozzles having a horizontal portion extending in a horizontal
direction and a vertical portion rising in a vertical direction,
said horizontal portion being attached to a sidewall of said
reaction container such that the horizontal portion penetrates the
sidewall of the reaction container, said vertical portion being
disposed in said reaction container apart from an inner wall of
said reaction container such that a portion of the vertical portion
is opposed to said heater disposed to heat the plurality of the
substrates, a flow-path cross-sectional area of the portion of the
vertical portion opposed to at least the heater being greater than
a flow-path cross-sectional area of the horizontal portion, a
flow-path cross-sectional shape of the portion of said vertical
portion that is opposed to at least said heater being formed into a
substantially elliptic shape with a short axis thereof oriented
toward a central portion of the substrate; and transferring the
processed plurality of substrates out from the reaction
container.
5. A substrate processing apparatus, comprising: a reaction
container to process a plurality of substrates; a heater to heat
the plurality of substrates; and a first nozzle and at least one
second nozzle to supply reaction gas into the reaction container,
wherein the first nozzle is attached to a sidewall of said reaction
container with said first nozzle penetrating the sidewall of said
reaction container and is disposed in the reaction container such
that the first nozzle is not opposed to the heater, the at least
one second nozzle comprises a plurality of nozzles having different
lengths, each of the plurality of nozzles includes a horizontal
portion extending in a horizontal direction and a vertical portion
rising in a vertical direction, said horizontal portion is attached
to a sidewall of said reaction container with said horizontal
portion penetrating the sidewall of said reaction container, said
vertical portion is disposed in the reaction container apart from
an inner wall of said reaction container such that a portion of the
vertical portion is opposed to the heater, a flow-path
cross-sectional area of the portion of the vertical portion that is
opposed to at least the heater is greater than a flow-path
cross-sectional area of the horizontal portion and a flow-path
cross-sectional area of the first nozzle, and a flow-path
cross-sectional shape of the portion of said vertical portion that
is opposed to at least said heater is formed into a substantially
elliptic shape with a short axis thereof oriented toward a central
portion of the substrate.
6. A producing method of a semiconductor device, comprising:
loading at least one substrate into a reaction container;
processing the at least one substrate by supplying reaction gas
into the reaction container heated by a heater through a first
nozzle, and a second nozzle, the first nozzle being attached to a
sidewall of said reaction container with said first nozzle
penetrating the sidewall of said reaction container and being
disposed in the reaction container such that the first nozzle is
not opposed to the heater, the second nozzle comprising a plurality
of nozzles having different lengths, each of the plurality of
nozzles including a horizontal portion extending in a horizontal
direction and a vertical portion rising in a vertical direction,
said horizontal portion being attached to a sidewall of said
reaction container with said horizontal portion penetrating the
sidewall of said reaction container, said vertical portion being
disposed in the reaction container apart from an inner wall of said
reaction container such that a portion of the vertical portion is
opposed to the heater, a flow-path cross-sectional area of the
portion of the vertical portion that is opposed to at least the
heater being greater than a flow-path cross-sectional area of the
horizontal portion and a flow-path cross-sectional area of the
first nozzle, a flow-path cross-sectional shape of the portion of
said vertical portion that is opposed to at least said heater being
formed into a substantially elliptic shape with a short axis
thereof oriented toward a central portion of the substrate; and
unloading the at least one substrate from the reaction container
after the processing.
Description
TECHNICAL FIELD
The present invention relates to a substrate processing apparatus,
and more particularly, to a substrate processing apparatus such as
a vertical CVD (Chemical Vapor Deposition) apparatus which produces
a semiconductor device such as an IC on a substrate such as a
silicon wafer.
BACKGROUND ART
As the substrate processing apparatus, there is a batch type
substrate processing apparatus which processes a necessary number
of substrates at a time, e.g., a vertical CVD apparatus which has a
vertical reaction furnace and which processes a necessary number of
substrates at a time.
For producing semiconductor devices, a batch type vertical hot wall
decompression CVD apparatus is widely used for forming a CVD film
such a polycrystalline silicon film, a silicon nitride film and the
like on a substrate (wafer).
A general batch type vertical hot wall decompression CVD apparatus
includes a reaction tube comprising an inner tube and an outer tube
which is concentric with the inner tube, a heater which is disposed
such as to surround the outer tube and which heats the inside of
the reaction tube, a gas introducing nozzle through which reaction
gas is introduced into the inner tube, and a vertical furnace
comprising an exhaust port or the like through which the reaction
tube is evacuated. A necessary number of multi-stacked wafers are
held in their horizontal postures and in this state, the wafers are
brought into the inner tube from below. Reaction gas is introduced
into the inner tube through the gas introduction nozzle, and the
inside of the reaction tube is heated by the heater, thereby
forming CVD films on the wafers.
As such a conventional substrate processing apparatus, there is a
vertical CVD apparatus as described in Japanese Patent Application
Laid-open No. 2000-68214 for example.
This vertical CVD apparatus includes a plurality of reaction gas
supply nozzles as the gas introducing nozzle. A quartz tube having
1/4 inch diameter (outer diameter) is used as the reaction gas
supply nozzle. Each reaction gas supply nozzle comprises a
horizontal portion which is inserted below the inner tube from the
horizontal direction, and a vertical portion which extends upward
along an inner surface of the inner tube, and the reaction gas
supply nozzle is formed into L-shape. The vertical portion is
provided in a gap between the inner tube, a boat and a wafer held
by the boat. An upper end of the vertical portion is opened.
Lengths of vertical portions of the respective reaction gas supply
nozzles are different from one another in stages so that reaction
gas can be dispersed and supplied into the inner tube.
When a CVD film is to be formed on a wafer, a reaction product is
formed not only on the wafer surface, but is also adhered to and
deposited on an inner surface of the inner tube 3 or an interior of
the reaction gas supply nozzle 106 as shown in FIG. 13. Especially
a portion of the reaction gas supply nozzle 106 that is opposed to
the heater 5 is heated by the heater 5 and thus, there is a high
tendency that the reaction product 47 is adhered to and deposited
on this portion of the reaction gas supply nozzle 106. Further,
since the pressure in the reaction gas supply nozzle 106 is higher
than the pressure outside of the nozzle 106, a reaction product 47
adhered to an inner wall of the nozzle 106 is three to four times
thicker than a reaction product adhered to an outer wall of the
nozzle 106. For this reason, when a flat polycrystalline silicon
film (this will be described later) having about 5,000 to 10,000
.ANG. thickness is to be formed using a quartz tube having 1/4 inch
diameter (outer diameter) as the nozzle 106, the nozzle 106 is
clogged during processing of three to four batches. In this case,
cleaning of the nozzle can not be carried out, and the only way is
to replace the nozzle 106 with a clean one every three to four
times batch processing. Therefore, maintenance operation such as
cleaning of the reaction gas supply nozzle must frequently be
carried out under the necessity, and this deteriorates the rate of
operation and throughput of the substrate processing apparatus.
In view of such circumstances, it is a main object of the present
invention to prevent a gas introducing nozzle from being clogged
soon even if a thick film such as a thick polycrystalline silicon
film is formed, to elongate a maintenance cycle, to reduce downtime
of the apparatus, to lighten the maintenance operation, and to
enhance the throughput.
DISCLOSURE OF THE INVENTION
According to an aspect of the present invention, there is provided
a substrate processing apparatus characterized by comprising:
a reaction container which processes a plurality of substrates;
a heater which heats said plurality of substrates; and
at least one nozzle through which reaction gas is supplied into
said reaction container, wherein said nozzle is attached to said
reaction container with said nozzle penetrating a wall of said
reaction container, and a flow-path cross-sectional area of a
portion of said nozzle that is opposed to at least said heater is
greater than a flow-path cross-sectional area of the
nozzle-attaching portion.
According to another aspect of the present invention, there is
provided a producing method of a semiconductor device characterized
by comprising:
a step for transferring a substrate or a substrates into a reaction
container,
a step for processing the substrate or substrates by supplying
reaction gas into a reaction container through a nozzle which is
attached to said reaction container such that the nozzle penetrates
a wall of the reaction container and in which a flow-path
cross-sectional area of a portion of the nozzle opposed to at least
a heater is greater than a flow-path cross-sectional area of the
attaching portion, and
a step for transferring the processed substrate or substrates out
from the reaction container.
BRIEF DESCRIPTION OF THE FIGURES IN THE DRAWINGS
FIG. 1 is a schematic longitudinal sectional view for explaining a
vertical CVD apparatus according to one example of the present
invention.
FIG. 2 is a transversal sectional view for explaining the vertical
CVD apparatus according to the one example of the present
invention.
FIG. 3 is a partially enlarged longitudinal sectional view of FIG.
1.
FIG. 4A is a sectional view taken along a line A-A in FIG. 3.
FIG. 4B is a sectional view taken along a line B-B in FIG. 3.
FIG. 5 shows variation in thicknesses of films formed on wafers
when batch processing is carried out in the substrate processing
apparatus according to the one example of the present
invention.
FIG. 6 is a schematic partial vertical sectional view for
explaining a state in which reaction product adheres to a gas
introduction nozzle.
FIG. 7 is a schematic partial vertical sectional view for
explaining a modification of the gas introduction nozzle.
FIG. 8A is a sectional view taken along a line A-A in FIG. 3 for
explaining a modification of the gas introduction nozzle.
FIG. 8B is a sectional view taken along a line B-B in FIG. 3 for
explaining a modification of the gas introduction nozzle.
FIG. 9A is a sectional view taken along a line A-A in FIG. 3 for
explaining a modification of the gas introduction nozzle.
FIG. 9B is a sectional view taken along a line B-B in FIG. 3 for
explaining a modification of the gas introduction nozzle.
FIG. 10A is a sectional view taken along a line A-A in FIG. 3 for
explaining a modification of the gas introduction nozzle.
FIG. 10B is a sectional view taken along a line B-B in FIG. 3 for
explaining a modification of the gas introduction nozzle.
FIG. 11A is a sectional view taken along a line A-A in FIG. 3 for
explaining a modification of the gas introduction nozzle.
FIG. 11B is a sectional view taken along a line B-B in FIG. 3 for
explaining a modification of the gas introduction nozzle.
FIG. 12A is a sectional view taken along a line A-A in FIG. 3 for
explaining a modification of the gas introduction nozzle.
FIG. 12B is a sectional view taken along a line B-B in FIG. 3 for
explaining a modification of the gas introduction nozzle.
FIG. 13 is a schematic partial longitudinal sectional view for
explaining a conventional vertical CVD apparatus.
PREFERABLE MODE FOR CARRYING OUT THE INVENTION
A preferred embodiment of the present invention will be explained
with reference to the drawings below.
Usually, when a polycrystalline silicon film is to be formed,
SiH.sub.4 is supplied as reaction gas from a reaction gas supply
nozzle. An inside of a furnace is heated to 610.degree. C., the
pressure in the furnace is maintained at 26.6 Pa and the film is
formed.
A flat polycrystalline silicon film is formed for a back seal of a
silicon wafer in some cases. In this case, the processing
temperature is higher by 30.degree. C. to 50.degree. C. as compared
with normal processing, and this film is formed thicker than the
polycrystalline silicon film.
This preferable embodiment of the invention is suitably used for
forming such polycrystalline silicon film and flat polycrystalline
silicon film and among them, this embodiment is suitably used for
forming especially the flat polycrystalline silicon film.
FIG. 1 schematically shows a batch type vertical CVD apparatus
which is one of substrate processing apparatuses, especially a CVD
apparatus which forms a flat polycrystalline silicon film,
especially a reaction furnace 1. FIG. 2 is a schematic transverse
sectional view for explaining especially the outline of the
reaction furnace 1.
Here, the term "flat" means that the temperature gradient in the
furnace is set flat (substantially zero). Therefore, flat
polycrystalline silicon films are polycrystalline silicon films
formed on a plurality of substrates disposed in a furnace in which
the temperature gradient is set flat. When the flat polycrystalline
silicon film is to be formed, film-forming gas is uniformly
supplied to the entire region in the furnace in which a plurality
of substrates are disposed and thus, a film-forming gas nozzle
called a long nozzle is used. Here, the term "long nozzle" means a
film-forming gas nozzle capable of supplying film-forming gas not
from outside of a region in the furnace where a plurality of
substrates are disposed but from inside of the region in the
furnace where the substrates are disposed. In the reaction furnace
of the vertical CVD apparatus, since this long nozzle is usually
inserted from a lower portion of the furnace and is extended toward
an upper portion of the furnace, the long nozzle is longer than a
normal nozzle which is inserted from the lower portion within the
furnace and terminated therein. To form the flat polycrystalline
silicon film, a plurality of, e.g., four quartz long nozzles which
extend along a region in the furnace where the plurality of
substrates are disposed and which have different lengths are
used.
With reference to FIGS. 1 and 2, an upper portion of an evacuation
air-tight chamber (not shown) such as a load lock chamber is
air-tightly provided with a stainless steel furnace opening flange
2 which forms a furnace opening. An inner tube 3 is concentrically
supported at a desired position of an inner surface of the furnace
opening flange 2, an outer tube 4 is provided on an upper end of
the furnace opening flange 2 concentrically with the inner tube 3.
A cylindrical heater 5 is provided concentrically with the outer
tube 4 such as to surround the outer tube 4. Heat insulators 44 are
provided such as to cover a periphery and an upper portion of the
heater 5. The heater 5 is divided into five zones, i.e., U, CU, C,
CL and L. When substrates are to be processed, a main control unit
24 controls such that temperatures of the five zones become the
same (temperature gradient becomes flat in the vertical direction).
A lower end of the furnace opening flange 2 is air-tightly closed
by a seal cap 13.
The inner tube 3 is of cylindrical shape whose upper and lower ends
are opened. The inner tube 3 is made of quartz or silicon carbide
which has heat resistance property and which does not contaminate
wafers. The wafers are heated equally by accumulating heat from the
heater 5, thereby equalizing heating effect of wafers. The outer
tube 4 is of a bottomed cylindrical shape having an opened lower
end and a closed upper end. Like the inner tube 3, the outer tube 4
is made of quartz or silicon carbide.
A boat 26 is provided in the inner tube 3. A plurality of wafers 30
are loaded on the boat 26 in their horizontal postures.
Predetermined gaps are provided between the wafers 30. The boat 26
is mounted on a boat-receiving stage 15 mounted on the seal cap 13.
The seal cap 13 on which the boat 26 is mounted moves upward, and
the lower end of the furnace opening flange 2 is air-tightly
closed. In this state, the wafers 30 loaded on the boat 26 are
located at predetermined positions. A plurality of heat insulative
plates 41 are placed on a lower portion of the boat 26, 5 to 10
dummy wafers 312 are placed thereon, one monitor wafer 325 is
placed thereon, 25 product wafers 304 are placed thereon, one
monitor wafer 324 is placed thereon, 25 product wafers 303 are
placed thereon, one monitor wafer 323 is placed thereon, 25 product
wafers 302 are placed thereon, one monitor wafer 322 is placed
thereon, 25 product wafers 301 are placed thereon, one monitor
wafer 321 is placed thereon, and 5 to 10 dummy wafers 311 are
placed thereon.
The inner tube 3 and the outer tube 4 constitute a reaction tube.
The furnace opening flange 2, the inner tube 3, the outer tube 4,
the heater 5 and the like constitute a vertical furnace. A
processing chamber 16 is defined in the inner tube 3. A cylindrical
gas discharge passage 11 is defined between the inner tube 3 and
the outer tube 4. The reaction tubes 3 and 4, the furnace opening
flange 2, the seal cap 13 and the like constitute the reaction
container.
A plurality of (four in the drawing) gas introducing nozzles 6, 7,
8 and 9 air-tightly penetrate a wall of the furnace opening flange
2 from the horizontal direction, and extend upward along an inner
surface of the inner tube 3, preferably in parallel to an axis of
the inner tube 3. The gas introducing nozzles 6, 7, 8 and 9 are
made of quartz, and upper ends of the gas introducing nozzles 6, 7,
8 and 9 are opened as gas ejection ports 63, 73, 83 and 93,
respectively. Reaction gas is introduced into the inner tube 3
through the gas introducing nozzles 6, 7, 8 and 9. The gas
introducing nozzles 6, 7, 8 and 9 penetrate the wall of the furnace
opening flange 2 at the same height in the horizontal direction but
lengths of the gas introducing nozzles 6, 7, 8 and 9 are different
from one another. The gas introducing nozzles 6, 7, 8 and 9
respectively comprise tube shaft intersecting portions 61, 71, 81
and 91 which intersect with an axis of the reaction tube, and a
tube shaft parallel portions 62, 72, 82 and 92 provided along a
tube inner surface in parallel to the axis of the reaction tube.
Lengths of the tube shaft parallel portions 62, 72, 82 and 92 are
different from one another in stages. As a result, heights of upper
end positions (gas ejection ports 63, 73, 83 and 93) of the gas
introducing nozzles 6, 7, 8 and 9 are different from one another in
stages.
The reason why the heights of the gas ejection ports 63, 73, 83 and
93 of the upper ends of the gas introducing nozzles 6, 7, 8 and 9
is that in order to secure the uniformity of film thicknesses of
the plurality of wafers 30 while setting the temperature gradient
in a direction along the tube axis in the reaction furnace 1 to
zero, it is necessary to divide a region where the plurality of
wafers 30 are disposed into four zones (product wafers 301, 302,
303 and 304), to allow the plurality of gas introducing nozzles 6,
7, 8 and 9 to extend into the reaction furnace 1 such as to
correspond to the divided zones respectively, and to supply the
reaction gas therefrom.
The gas ejection ports 63, 73, 83 and 93 of the upper ends of the
gas introducing nozzles 6, 7, 8 and 9 are disposed at equal
distances from one another. The gas ejection ports 63, 73, 83 and
93 are located in the vicinity of central portions of arrangement
regions of product wafers 301, 302, 303 and 304 on which 25 wafers
are stacked, respectively. Since the gas ejection ports 63, 73, 83
and 93 of the upper ends of the gas introducing nozzles 6, 7, 8 and
9 are positioned such as to respectively correspond to the product
wafers 301, 302, 303 and 304 of the four zones in the processing
chamber 16, reaction gas is equally supplied to the plurality of
wafers 30.
Reaction gas is consumed by forming films, but since the gas
ejection ports 63, 73, 83 and 93 of the upper ends of the gas
introducing nozzles 6, 7, 8 and 9 are opened upward in stages,
reaction gas is introduced in succession to compensate the consumed
reaction gas. The reaction gas is introduced in equal
concentrations from the lower portion to the upper portion of the
processing chamber 16 and as a result, film thicknesses of the
wafers 30 are equalized.
As shown in FIG. 2, the gas introducing nozzles 6, 7, 8 and 9 are
disposed on the same circumference at equal distances from one
another along the inner surface of the inner tube 3. To facilitate
the understanding of explanation, the inner tube 3 is disposed in
the radial direction in FIG. 1. A gas introduction nozzle 10 is a
straight nozzle which intersects with the tube axis. The gas
introduction nozzle 10 is made of quartz like the gas introducing
nozzles 6, 7, 8 and 9.
As shown in FIGS. 3, 4A and 4B, the tube shaft intersecting
portions 61, 71, 81 and 91 of the gas introducing nozzles 6, 7, 8
and 9 have small diameters (small flow-path cross sections).
Portions of the tube shaft parallel portions 62, 72, 82 and 92
which are opposed at least to the heater 5 have large diameters
(large flow-path cross sections). A flow-path cross-sectional area
of the large-diameter portion is preferably at least two times or
more of the flow-path cross-sectional area of the small-diameter
portion.
Concerning a method for obtaining the large flow-path cross
section, inner diameters of the tube shaft parallel portions 62,
72, 82 and 92 are increased with respect to the tube shaft
intersecting portions 61, 71, 81 and 91. If the diameters of the
tube shaft intersecting portions 61, 71, 81 and 91 are reduced to
small values (in this embodiment, 1/4 inches, the same as the
conventional outer diameter), this method can be carried out
without largely modifying the existing substrate processing
apparatus. As shown in FIGS. 4A and 4B, the cross-sectional shapes
of the tube shaft parallel portions 62, 72, 82 and 92 are formed
into a long circle or ellipse (elliptic shape) having long shaft in
the circumferential direction. In this case, outer diameters of
thereof in the directions of the short axes are set to the same
sizes as those of the tube shaft intersecting portions 61, 71, 81
and 91, or determined so that the tube shaft parallel portions 62,
72, 82 and 92 do not interfere with the boat 26 and the wafer 30
while taking into consideration the inner tube 3 and the boat 26,
as well as the gaps between the wafers 30 held by the boat 26. In
this embodiment, the cross sections of the tube shaft intersecting
portions 61, 71, 81 and 91 are circular having outer diameters of 5
to 7 mm and inner diameters of 3 to 5 mm. Outer diameters "b" of
the tube shaft parallel portions 62, 72, 82 and 92 in the short
axis direction are 7 to 9 mm, and inner diameters "a" are 5 to 7
mm. Outer diameters "d"of the tube shaft parallel portions 62, 72,
82 and 92 in the long axis direction are 10 to 12 mm, and inner
diameters "c" are 8 to 10 mm.
In this embodiment, the inner diameters of the tube shaft parallel
portions 62, 72, 82 and 92 are increased with certain inclination
from a portion 51 at which the inner diameters start increasing,
and the inner diameters become constant from a portion 52. This
portion 52 is located lower than a lower end 53 of the heater 5.
The portion 51 at which the inner diameters start increasing is
located lower than the heater 5, the outer tube 4 and the heat
insulative plates 41, and is higher than lower ends of the
boat-receiving stage 15 and the inner tube 3, and is located within
a region opposed to the furnace opening flange 2.
As shown in FIG. 7, the portion 52 at which the inner diameters
finish increasing may be at substantially the same height as the
lower end 53 of the heater 5 (see (a)), the portion 51 at which the
inner diameters start increasing may be at substantially the same
height as the lower end 53 of the heater 5 (see (b)), and a portion
at which the inner diameters are increasing may be at substantially
the same height as the lower end 53 of the heater 5 (see (c)). The
inner diameters of the tube shaft parallel portions 62, 72, 82 and
92 may not be increased with the certain inclination from the
portion 51 at which the inner diameters start increasing, but the
inner diameters may be increased suddenly at the portion 54. In
this case, the portion 54 may be lower than the lower end 53 of the
heater 5 (see (d)), or may be substantially at the same height as
the lower end 53 of the heater 5 (see (e)). The upper ends of the
tube shaft parallel portions 62, 72, 82 and 92 may not be provided
with the gas ejection ports 63, 73, 83 and 93. Alternatively,
porous nozzles (see (f)) provided a plurality of gas ejection ports
48 on side surfaces of the tube shaft parallel portions 62, 72, 82
and 92 may be used. In this case, positions of the portions 51 and
52 are the same as those of the gas introducing nozzles 6, 7, 8 and
9.
Referring back to FIG. 3, the tube shaft parallel portions 62, 72,
82 and 92 and the tube shaft intersecting portions 61, 71, 81 and
91 may be connected to each other as separate parts or they may be
integrally formed together.
Cushion members 46 are respectively mounted on lower portions of
the tube shaft intersecting portions 61, 71, 81 and 91. The cushion
members 46 are in contact with a metal ring nozzle support member
45 which is mounted such as to project inward from a wall of the
furnace opening flange 2.
The furnace opening flange 2 is provided with an exhaust tube 12
which is in communication with a lower end of the gas discharge
passage 11. Reaction gas introduced from the gas introducing
nozzles 6, 7, 8, 9 and 10 flows upward in the inner tube 3, the
reaction gas is turned back at the upper end of the inner tube 3,
and flows downward in the gas discharge passage 11, and is
discharged out from the exhaust tube 12.
Referring back to FIG. 1, an opening (furnace opening) of the lower
end of the furnace opening flange 2 is air-tightly closed with the
seal cap 13. The seal cap 13 is provided with a boat-rotating
apparatus 14. The boat 26 stands on the boat-receiving stage 15
which is rotated by the boat-rotating apparatus 14. The seal cap 13
is supported by a boat elevator 17 such that the seal cap 13 can
move vertically.
The gas introducing nozzles 6, 7, 8, 9 and 10 are connected to a
reaction gas supply source 42 which supplies reaction gas such as
SiH.sub.4 or the like, or are connected to a purge gas supply
source 43 which supplies inert gas such as nitrogen gas
respectively through mass flow controllers 18, 19, 20, 21 and 22 as
flow rate controllers.
The main control unit 24 control the heating operation of the
heater 5, the vertical movement of the boat elevator 17, rotation
of the boat-rotating apparatus 14, and flow rates of the mass flow
controllers 18, 19, 20, 21 and 22. A temperature detection signal
from one or more temperature detectors 25 which detect the
temperature in the furnace is input to the main control unit 24,
and the heater 5 is controlled such that the heater 5 equally heats
inside of the furnace.
The operation will be explained below.
The boat 26 is lowered by the boat elevator 17, and wafers 27 are
loaded on the lowered boat 26 by a substrate loader (not shown). In
a state in which a predetermined number of wafers 27 are loaded,
the boat elevator 17 moves the seal cap 13 upward to bring the boat
26 into the processing chamber 16. The processing chamber 16 is
air-tightly closed with the seal cap 13, the processing chamber 16
is decompressed to a processing pressure through the exhaust tube
12, and the processing chamber 16 is heated to the processing
temperature by the heater 5. The boat 26 is rotated around the
vertical axis by the boat-rotating apparatus 14.
The mass flow controllers 18, 19, 20, 21 and 22 control the flow
rate of the reaction gas (SiH.sub.4), and the reaction gas is
introduced into the processing chamber 16 through the gas
introducing nozzles 6, 7, 8, 9 and 10. The reaction gas (SiH.sub.4)
may be 100% SiH.sub.4 and introduced alone, or SiH.sub.4 may be
diluted with N.sub.2 and introduced.
During the process in which reaction gas flows upward in the
processing chamber 16, reaction product is deposited on the wafers
27 by thermochemical reaction and films are formed. Since the boat
26 is rotated, the reaction gas is prevented from unevenly flowing
with respect to the wafers 27.
Reaction gas is consumed by forming films, but since the upper end
positions (gas introducing positions) of the gas introducing
nozzles 6, 7, 8 and 9 are opened upward in stages, reaction gas is
introduced in succession to compensate the consumed reaction gas.
The reaction gas is introduced in equal concentrations from the
lower portion to the upper portion of the processing chamber 16.
Therefore, film thicknesses of the wafers are equalized.
The mass flow controllers 18, 19, 20, 21 and 22 control the amount
of gas to be introduced from the gas introducing nozzles 6, 7, 8, 9
and 10 such that the concentration of reaction gas becomes
constant.
Reaction gas is heated by the heater 5 during the process in which
the reaction gas passes through the tube shaft intersecting
portions 61, 71, 81 and 91 and flows upward in the tube shaft
parallel portions 62, 72, 82 and 92. Therefore, while the reaction
gas passes through the tube shaft parallel portions 62, 72, 82 and
92, reaction product adheres to inner surfaces of the tube shaft
parallel portions 62, 72, 82 and 92 in some cases. As described
above, portions of the tube shaft parallel portions 62, 72, 82 and
92 which are opposed at least to the heater 5 are large in
diameters. Thus, even if reaction product 47 adheres as shown in
FIG. 6, the gas introducing nozzles 6, 7, 8 and 9 are not
clogged.
Further, since the temperatures in the tube shaft intersecting
portions 61, 71, 81 and 91 are low and reaction does not proceed
and thus, the diameters of the tube shaft intersecting portions 61,
71, 81 and 91 may be left thin. As shown in FIG. 3, joint portion
areas between the tube shaft intersecting portions 61, 71, 81 and
91 and the tube shaft parallel portions 62, 72, 82 and 92, or
portions of the tube shaft parallel portions 62, 72, 82 and 92
which are not opposed to the heater 5 and which rise from the tube
shaft intersecting portions 61, 71, 81 and 91 are small in
diameters because temperatures thereof are less than 300 to
400.degree. C. and reaction does not proceed.
Even the portions of the tube shaft parallel portions 62, 72, 82
and 92 opposed to the heater 5, temperatures in lower portions of
these portion are less than 300 to 400.degree. C. and these
portions are not heated so much and thus, these lower portion may
be left small in diameters. Portions of the tube shaft parallel
portions 62, 72, 82 and 92 which are increased on flow-path cross
sections and which are opposed to the heater 5 maybe defined as
regions where the wafers 30 are accommodated.
Therefore, even when films are repeatedly formed, clogging of the
nozzle can be suppressed, the supply amount of reaction gas from
the gas introducing nozzles 6, 7, 8 and 9 does not become
insufficient, and substrates can be processed with excellent
quality. Effect can be expected in forming processing of
polycrystalline silicon thick film, preferably flat polycrystalline
silicon thick film. The present invention can also be applied to
forming processing of SiGe films which is carried out using
silane-based gas such as SiH.sub.4 and germane-based gas such as
GeH.sub.4.
A portion of the nozzle where it is required to increase a
flow-path cross-sectional area is a portion whose temperature
becomes such a degree that film-forming reaction is generated
(portion where its temperature becomes 300 to 400.degree. C. or
higher in the case of SiH.sub.4), or a portion whose temperature
becomes such a degree that reaction gas is dissolved (portion where
its temperature becomes 300 to 400.degree. C. or higher in the case
of SiH.sub.4).
A portion of the nozzle where it is not required to increase the
flow-path cross-sectional area is a nozzle-attaching portion, a
nozzle horizontal portion, a nozzle bent portion, a portion which
is not opposed to the heater, and a portion whose temperature
becomes such a degree that film-forming reaction is not generated
(portion where its temperature becomes less than 300 to 400.degree.
C. in the case of SiH.sub.4), or a portion whose temperature
becomes such a degree that reaction gas is not dissolved (portion
where its temperature becomes less than 300 to 400.degree. C. in
the case of SiH.sub.4).
FIG. 5 shows variation in thicknesses of films formed on wafers
when batch processing is carried out in a substrate processing
apparatus of the present invention.
Preferable processing conditions are that film-forming temperature,
i.e., temperature in a region of at least the processing chamber 16
where the wafers 30 are accommodated is 650 to 670.degree. C.,
film-forming pressure is 10 to 30 Pa, thickness of formed film is
5,000 to 10,000 .ANG., and reaction gas flow rate (SiH.sub.4, total
flow rate: 0.2 to 1 SLM).
FIG. 5 shows a case in which the batch processing is repeated ten
times under the above processing conditions. There is a tendency
that the average film thickness (average film thickness value of
wafers subjected to the same batch processing) is gradually
increased with each batch processing, but the uniformity of film
thicknesses with each batch processing is .+-.0.38% and falls
within a range where product quality is not harmed, clogging of the
nozzle can be suppressed, and the supply amount of reaction gas
does not become insufficient. Conventionally, the nozzle is clogged
after batch processing is repeated three to four times, but
according to this embodiment, it has been confirmed that the batch
processing can be carried out ten or more times.
If the mass flow controllers 18, 19, 20, 21 and 22 are controlled
by collecting data concerning uniformity of film thicknesses with
every batch processing and by grasping the tendency, and if the
flow rate is controlled with each batch processing, the uniformity
of film thicknesses is enhanced.
Although the film-forming temperature is 650 to 670.degree. C. in
the above embodiment, the film-forming temperature may be
620.degree. C. or higher. For example, the film-forming temperature
may be 620 to 680.degree. C. The tube shaft parallel portions 62,
72, 82 and 92 can be produced by crushing tubes of 3/8 inches for
example. Cross-sectional shapes of the tube shaft parallel portions
are not limited to circular, long circular or elliptic shape. The
cross-sectional shape may be arc long circular shape or a
rectangular having long sides in the circumferential direction. In
short, the cross-sectional shape is not limited only if the
flow-path cross section can be enlarged. Preferable examples of the
cross-sectional shape are squashy circular shape, substantially
elliptic shape, crushed circular shape (elliptic shape, egg-like
shape, rounded rectangular shape, shape in which ends of opposed
semi-circles are connected with each other through straight lines),
substrate elliptic shape in which short axis is oriented toward a
central portion of a substrate, a substantially elliptic shape
having short axis in a direction of a straight line which connects
a center of a substrate and a center of a nozzle, a substantially
elliptic shape having long axis in a direction substantially
perpendicular to a straight line which connects the center of the
substrate and the center of the nozzle, a shape in which a width in
a direction of a straight line which connects the center of the
substrate and the center of the nozzle is smaller than a width in a
direction which is substantially perpendicular to the former width,
a rectangular shape having long sides in a direction substantially
perpendicular to the straight line which connects the center of the
substrate and the center of the nozzle, and a rhombus shape having
long sides in a direction substantially perpendicular to the
straight line which connects the center of the substrate and the
center of the nozzle. FIGS. 8A to 12B show such modifications.
The present invention can also be carried out even if the reaction
furnace is a lateral reaction furnace.
As explained above, in this embodiment, the flow-path
cross-sectional area of a portion of the nozzle that is opposed at
least to the heater is set greater than the flow-path
cross-sectional area of the attaching portion of the nozzle on the
reaction container. Therefore, it is possible to suppress the
clogging of the nozzle, and to increase the number of processing
which can be carried out until maintenance is required. With this,
a frequency of the maintenance can be reduced (maintenance cycle
can be increased), and downtime of the apparatus can be
reduced.
The flow-path cross-sectional area of the attaching portion of the
nozzle on the reaction container is not increased and the same
shape as that of the conventional technique (1/4 inch diameter) can
be employed and thus, a furnace opening flange having the same
shape as that of the conventional technique (corresponding to
nozzle of 1/4 inch diameter) can be used as it is, and it is
unnecessary to newly design the furnace opening flange. When the
flow-path cross-sectional area of the entire nozzle is increased,
it is necessary to newly design (change the design of) the furnace
opening flange such in accordance with the changed nozzle
shape.
Since the cross-sectional shape of the portion of the nozzle that
is opposed to the heater is the squashy circular shape (elliptic
shape), clearance between the wafer and the inner tube can be
reduced. With this, the gas concentration over the entire surface
of a substrate can be equalized, and uniformity of film thickness
over the entire surface of the substrate and uniformity of film
quality over the entire surface of the substrate can be enhanced.
Further, the volume of the reaction tube can be reduced, and an
amount of gas to be used can be saved. Further, the apparatus can
be reduced in size.
The entire disclosures of Japanese Patent Application No.
2003-206526 filed on Aug. 7, 2003 and Japanese Patent Application
No. 2004-096063 filed on Mar. 29, 2004 each including
specification, claims, drawings and abstract are incorporated
herein by reference in those entirety.
Although various exemplary embodiments have been shown and
described, the invention is not limited to the embodiments shown.
Therefore, the scope of the invention is intended to be limited
solely by the scope of the claims that follow.
INDUSTRIAL APPLICABILITY
As explained above, according to the embodiment of the present
invention, in a substrate processing apparatus having a reaction
tube which processes a plurality of substrates, a heater which
heats the substrates, and at least one gas introduction nozzle
through which gas is supplied into the reaction tube, a flow-path
cross section of a portion of the gas introduction nozzle that is
opposed at least the heater is greater than flow-path cross section
of other portion. Therefore, it is possible to exhibit excellent
effects that when films are to be formed, clogging of the gas
introduction nozzle can be suppressed, maintenance operation is
reduced, maintenance cycle can be shortened, and throughput can be
enhanced.
As a result, the present invention can suitably be utilized
especially for a vertical CVD apparatus which produces a
semiconductor device on a silicon wafer, and for a producing method
of a semiconductor device which uses this CVD apparatus.
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